Question

For a reversible gaseous reaction, $N _2+3 H _2 \rightleftharpoons 2 NH _3$ at equilibrium, if some moles of $H _2$ are replaced by same number of moles of $T _2$ ($T$ is tritium, isotope of $H$ and assume isotopes do not have different chemical properties) without affecting other parameter, then :

• A. the sample of ammonia obtained after sometime will be radioactive
• B. moles of $N _2$ after the change will be different as compared to moles of $N _2$ present before the change
• C. the value of $K_P$ or $K_c$ will change
• D. the average molecular mass of new equilibrium will be same as that of old eauilibrium

Answer 1

Answer: (A)

(a) The sample of ammonia obtained will be a mixture of $NH _3, NT _3, NH _2 T$ and $NHT _2$. Thus, this mixture will be radioactive.
(b) The position of equilibrium will not change by using isotopes.
(c) The value of equilibrium constant also remains same.
(d) Now the sample will contain tritium containing forms of ammonia and hydrogen $\left( H _2, HT\right.$ and $\left.T _2\right)$. Thus, the average molecular mass will increase.